Acoustic device



1 1927' H. c. HARRISON ACOUSTIC DEVICE Filed June 5, 1923 Patented Jan. 11, 1927.

PATENT OFFICE.

HENRY C. HARRISON, OF PORT WASHINGTON, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, mconrona'rnn, or NEW YORK, N.

N EW YORK.

Y.-, A CORPORATION OF ACOUSTIC DEVICE.

Application filed June 5,

This invention relates to acoustic devices and has for its object improvements in such devices, whereby sound vibrations in the audible range will be faithfully and etiicfiently transmitted.

In accordance with the general features of the invention there is provided a diaphragm substantially free at its periphery and a mounting therefor whereby the symmetry of the diaphragm is preserved by the application of uniformly distributed forces. In one of its embodiments the invention provides a large diaphragm. preferably of light elastic material of conoidal form supported against one or more cushions or networks of textile or other suitable material uniformly tensioned, whereby the circular symmetry of thediaphragm is maintained through the application of uniformly distributed forces 9 without substantially changing its mass.

Referring to the drawing:

Fig. 1 is a cross-sectional view of an acoustic device embodying the invention;

Fig. 2 is a rear view of the device on the line 2'2, showing a resilient cushion for the diaphragm;

Fig. 3 is a detail view of the support for the cushion:

Fig. 4 shows in detail a modification which may be used in place of the support shown in Fig. 3; I

Fig. 5 is a sectional view of the device on the line Fig. 1, showing additional means for adding stiffness to the diaphragm;

Fig. 6 shows an arrangement for supporting the networks shown in Fig. 5:

Fig. 7 shows an actuating device which mav be used.

An actuating device 10 is supported in a cabinet 11 by means of a bar 12. On a rod 13 carried by the vibrating system of the actuating element 10. is supported a diaphragm 14. which is preferably conical in shape and made of a light elastic material such as paper and of any size suitable for use in loud speaking apparatus. for example, between nine and thirty-six inches in diameter. A wall 15. having a circular opening therein of substantially the same diameter as that of the diaphragm 14 and coaxial therewith, carries on the rear thereof a plurality of supports 16 equally spaced on a circle concentric with the opening of the 1923. Serial No. 643,577.

wall 15. Preferably an odd number of supports 16 are provided, for example, twenty-tive, and a. thread 17, of any sultable material, preferably of silk, is woven around the supports, engaging each once and terminating at the starting support. Startin with the support A, for example, the threa 17 1s passed around B, C, D and E and maintamed taut. This is repeated until all of the supports have been used. falling back one step each revolution and finally terminating at the support A. This forms a resilient bridge, against which the periphery of the diaphragm 14 maybe supported. In one form the elements of a network so formed lie substantially in the same plane and are uniformly tensioned chords of substantially equal length of the same circle. The diaphragm 14 may be held against this network by applying a slight pressure, or tension in case the network is applied to the back of the diaphragm, at the apex of the diaphragm through the actuating device 10 or other suitable means. The pressure or the tension may be regulated by adjusting in any well known manner-the actuating device 10 in the support 12.v By this arrangement uniformly distributed forces are applied in the same plane to the diaphragm thereby preserving the shape of the diaphragm without increasing the mass of the vibrating system. The supports 16 are preferably of resilient material so as to compensate for any changes in the length of the thread 17 due to changes in atmospheric conditions.

Fig. 4 shows an alternative supporting arrangement employing a light spiral spring 18 for connecting the thread 17 to the stud 19.

A plurality of similarly formed networks 21, 22 and 23, having respectively graduated central openings therein, may also be supported in spaced relation against the outer surface of the diaphragm 14. Through these networks additional symmetrically disposed forces are applied to the diaphragm and assist in maintaining its symmetry without increasing the mass of the vibrating system. If desired. these networks may also be used to support the diaphragm in operative relation to the actuating device 10.. The networks 21, 22 and 23 may be formed in the same manner as the network 17 and may be supported in rings 24, 25 and 26, respectively, each of which may be supported in the case 11 by means of members 27, 28 and 29, respectively, in a manner such that each of the elements of the network presses slightly against the outer surface of the diaphragm.

Fig. 6 shows an arrangement employing springs 30 for supporting the networks 21, 22 and 23 in their respective frames.

The actuating device shown in Fig. preferably of 1,365,898 of Egerton.

Although the network 17 in the form described herein is preferable, as it gives a bridge of very slight mass, good results may be obtained by using a piece of fabric such as silk or linen stretched to form a bridge against which the diaphragm may be supported.

The invention claimed is:

1. An acoustic device comprising a large direct acting conical diaphragm of light flexible material, and tensioned means disposed against the outside surface s of said diaphragm for introducing a compressional strain therein.

2. An acoustic device comprising a large direct acting conical diaphragm of light flexible material, and light resilient means operating against the face of said diaphragm at its base to introduce a compressional strain therein and thereby preserve its symmetry while vibrating.

3. An acoustic device comprising a large conical diaphragm, a network of thread-like material, and means supporting said diaphragm against said network introducing a compressional strain in said diaphragm.

4. An acoustic device comprising a large conical diaphragm substantially free at its outside surface, a resilient bridge of circular form and of low mass, resilient means supporting said bridge and exerting tension therein, and means for holding said diaphragm in contact with said bridge thereby introducing a compressional strain in said diaphragm.

5. An acoustic device comprising a large conical diaphragm, a network of thread-like material, and means supporting said diaphragm against said network.

-6. An acoustic device comprising a large conical diaphragm, a network of uniformly 7 is the type shown in Patent No.

January 18, 1921, to H. (7.

tcnsioned material and means supporting said diaphragm against said network.

T. in acoustic device comprising an apcrtured tar-c. a network in space relation with said tat-c, a conical diaphragm peripherally disposed against said network, and an actuating device opcratively associated with and supporting said diaphragm.

8. An acoustic device comprising a conical diaphragm of light, flexible material substantially free at its periphery, a resilient cushion disposed against the concave side of said diaphragm and at the base thereof, and resilient means spaced from the base for supporting said diaphragm against said cushion.

9. An acoustic device comprising a large direct acting conical diaphragm of light flexible material having substantially a free edge and a plurality of spaced supports of substantially no mass having co-axial openings therein for receiving said diaphragm.

10. A acoustic device comprising a conical diaphragm, and a plurality of supporting networks having coaxial openings therein for receiving said diaphragm and holding it in shape.

11. An acoustic device comprising a conical diaphragm, a resilient cushion dis osed against the base of said diaphragm, a urality of networks of textile material aving graduated central openings therein and means for holding said networks in contact with said diaphragm.

12. An acoustic device comprisin a frame having an opening therein, a we means supporting said web adjacent said opening and exerting tension therein, a conical diaphragm having its concave side disposed against said web, and means spaced from the base of said diaphragm for exerting a slight pressure thereon and thereby preserving the symmetry of the diaphragm while vibrating.

13. The method of preserving the symmetry of a conical diaphragm while vibrating which consists in applying to the concave side of the diaphragm and parallel to the axis thereof a system of forces which are substantially without associated mass or elasticity for giving rigidity to the surface of the diaphragm.

In witness whereof, I hereunto subscribe my name this 1st day of June A. D., 1923.

HENRY G. HARRISON. 

